A blasting booster comprises a rigid tube filled with a mixture, by weight, of about: 60% to 80% ammonium nitrate prills ground through a 1/16" screen; 12% to 35% whole ammonium nitrate prills and 3% to 8% diesel oil. Preferably the mixture includes about 0.4% to 10% aluminum fuel and the weight ratio of ground to whole prills is about 4 to 1. In use the booster tube is plastic lined and is placed in the bottom of a bore hole which is filled with AN-FO or an appropriate blasting agent. A one-pound cast primer on top of the booster is detonated to initiate the booster and the AN-FO, whereby detonation velocities and pressures in excess of non-boosted AN-FO, for example, are achieved in the critical bottom three feet of the bore hole. Bore hole patterns, where the booster is used, are expanded over tighter patterns required for non-boosted AN-FO alone, and drilling costs are significantly reduced.